This invention relates to the production of methyl isobutyl ketone (MIBK) and diisobutyl ketone (DIBK) by the catalytic reaction of acetone (DMK) and/or isopropyl alcohol (IPA). More specifically, this invention relates to a method for altering the ratio of MIBK to DIBK produced by adjusting the reaction pressure.
MIBK and DIBK are important industrial solvents. As discussed in U.S. Pat. No. 5,925,796 (herein fully incorporated by reference) MIBK and DIBK can be co-produced by the catalyzed reaction of hydrogen and DMK and/or IPA. Typically, an aldol condensation catalyst is used. The MIBK to DIBK ratio is not constant and decreases as steps are taken to increase MIBK production by increasing reactant conversion. This phenomenon is illustrated in the FIGURE of the '796 patent, showing an empirically determined, fitted line which depicts the DIBK/MIBK ratio as a function of the MIBK produced. Unfortunately, the needs of the marketplace do not necessarily conform to the natural tendencies of the chemistry. Thus, if it is desired to increase the MIBK production to meet market demands, an excessive amount of DIBK may be produced, resulting in the need to store or destroy some of the DIBK, and to accept the related raw material inefficiencies and energy penalties. Accordingly, it would be very desirable to have a method whereby the DIBK/MIBK ratio is more readily controlled, permitting the manufacturing operation to, in effect, vary the amount of either material desired and also obtain a more desired amount of the other material, thereby “de-coupling” the usual relationship between the production levels of these two products. The '796 patent disclosed one solution to the above-stated problem. The instant invention provides an alternative or additional solution to this problem.